Laminar free convection in open-ended vertical 7-rod undles: numerical

Solely buoyancy induced flow and heat transfer have been investigated numerically in two open-ended 7-rod bundles of differing arrangements. The circular geometry of the six peripheral rods was replaced by equivalent curved trapezium to get rid of non-orthogonal intersections of the grid lines on the rod boundary. Solutions were initiated assuming a value of dimensionless inlet velocity and then progressed longitudinally until the pressure equals that of the ambient. The flat axial velocity profile at inlet gradually changes with the axial distance. The radial velocity profiles show the diminishing entry effects as the flow develops axially. At high heat input, the bundle height is insufficient for the flow to be fully developed. Numerically evaluated volume flow rates are in excellent agreement with the measured values for both the bundles under investigation.